1. Technical Field
The present invention relates to technology for controlling an external storage device with a plurality of storage units.
2. Related Art
So-called external hard disk drives used connected to a computer are becoming widespread. This hard disk drive is typically driven by commercial power or by power supplied from a computer via USB.
In recent years, large capacity external storage devices that have a plurality of hard disk drives built into one case have become widespread. With this kind of external storage device, in the past, technologies were proposed that would reduce power consumption by differentiating the uses of the plurality of hard disk drives. For example, in some technology, with a disk array device equipped with a plurality of hard disks or hard disk drives, when in the energy saving mode, there is differentiation of use of the plurality of hard disk drives based on the use information of the plurality of hard disks. Also, in another technology, with a disk array device equipped with a plurality of hard disks, when in energy saving mode, there is differentiation of use of the plurality of hard disks based on the load information.
However, with the above mentioned technology, there was no consideration made for differentiation of use of the plurality of hard disk drives in cases when it is not possible to operate all of the plurality of hard disk drives with the supplied power, for example, when the power is supplied by USB to the external storage device. Specifically, with the above mentioned technology, one or more hard disk drives sometimes stop operating, because the power supplied to the plurality of hard disk drives is insufficient.
The present invention was created to address the problems noted above, and an advantage of some aspects of the invention is as follows: when controlling an external storage device equipped with a plurality of storage units, the desired storage device can be operated, when it is possible to operate only part of the plurality of storage units by the power supplied to the external storage device.
The entire disclosure of Japanese patent application No. 2008-126890 of BUFFALO is hereby incorporated by reference into this document.